This is a simple alias to document.getElementById, which not only is shorter to write, but fortunately works in all
browsers. It turns a domNode reference to some Node byId, or the same node reference if passed a domNode.

require(["dojo/dom","dojo/domReady!"],function(dom){varoutput="";if(dom.isDescendant("child","ancestor")){output+="'child' is a descendant of 'ancestor'</br>";}else{output+="'child' is not a descendant of 'ancestor'</br>";}if(dom.isDescendant("loner","ancestor")){output+="'loner' is a descendant of 'ancestor'</br>";}else{output+="'loner' is not a descendant of 'ancestor'</br>";}dom.byId("output").innerHTML=output;});

Some basic HTML to facilitate the example.

<divid="ancestor"><divid="child">I'm a child!</div></div><divid="loner">I'm not a child!</div><divid="output"></div>